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Disc diffusion-based screening tests for extended-spectrum beta-lactamases in Haemophilus influenzae
Stephen G Tristram1, Bülent Bozdogan, Peter C Appelbaum
1School of Human Life Sciences, University of Tasmania, Launceston, Tasmania 7250, Australia. Stephen.Tristram@utas.edu.au
The Journal of Antimicrobial Chemotherapy
|February 25, 2005
Summary
This study identifies effective screening methods for extended-spectrum beta-lactamases (ESBLs) in Haemophilus influenzae. Prediffusion and combination discs reliably detect ESBL-producing strains, crucial for antibiotic resistance monitoring.
Area of Science:
- Microbiology
- Antimicrobial Resistance
- Clinical Diagnostics
Background:
- Extended-spectrum beta-lactamases (ESBLs) confer resistance to key antibiotics.
- Accurate detection of ESBLs in Haemophilus influenzae is essential for effective treatment.
- Current screening methods may require optimization for H. influenzae.
Purpose of the Study:
- To develop and validate a reliable screening test for ESBL detection in Haemophilus influenzae.
- To evaluate different disc diffusion methods for ESBL identification.
Main Methods:
- Screening involved double disc diffusion tests with cephalosporin and amoxicillin/clavulanate discs.
- Prediffusion tests and combination discs were assessed using recombinant and clinical H. influenzae strains.
- Validation included testing a range of clinical isolates.
Main Results:
- Standard double disc diffusion was unreliable for detecting ESBLs in recombinant H. influenzae.
- Prediffusion tests (cefotaxime/cefpodoxime with amoxicillin/clavulanate) and combination discs showed promise.
- A zone size increase of >= 5 mm compared to plain discs indicated ESBL presence in recombinant strains.
Conclusions:
- Prediffusion or combination disc methods are suitable for screening H. influenzae for ESBLs.
- Cefotaxime and cefpodoxime based tests demonstrated effectiveness.
- An increase in zone diameter of >= 5 mm is a key indicator for ESBL-producing strains.